Government regulations are requiring automobile manufacturers to provide passive restraint devices for automobile passengers in case of collision, and an inflatable bag between the passenger and the dashboard or the driver and the steering wheel appears suitable. Impact sensors are provided in the automobile and when a collision occurs, a gas system is activated for rapidly inflating the passenger restraint bag. Some such systems have employed stored pressurized gas which is suddenly released into the bag. Such systems have required very high pressures to obtain sufficient gas in a small enough volume. The stored volume of gas must be fairly high to compensate for the significant cooling that occurs upon rapid depressurization of the gas.
According to another technique, a propellant is burned to generate quantities of gas which are used to inflate the bag. Such gasses must enter the bag at a sufficiently low temperature that no injury occurs either to the passenger or to the bag. For similar reasons, hot particles must be prevented from entering the bag. The gasses that enter the bag are dissipated in the passenger compartment of the automobile and it is therefore necessary that they be nontoxic and substantially free of smoke.
To obtain high volumes of nontoxic gasses, a variety of deflagration propellants have been devised which react strong oxidizers with various organic materials. These combustions typically yield principally carbon dioxide and water vapor, often with an excess of oxygen for avoiding asphyxiation. In the progress of developing such propellants for practical systems, granular or powder mixtures of various oxidizers and organic materials have been provided.
A restraint system for the driver of a vehicle must be relatively small since the entire system is accommodated within the existing size envelope of the steering wheel. To fit in this envelope, the inflatable bag is folded to a compact volume with its mouth adjacent the gas generator. These bags are carefully folded in a pre-determined manner for orderly deployment and it has been found best to do this folding by hand. such manual bag folding may involve large numbers of people.
The pyrotechnic gas generators have some saftey hazard, particularly when accumulated in substantial numbers as would be required in a manufacturing operation. Folding the bags on loaded gas generators creates many logistics, facilities and safety problems.
It is desirable to provide an arrangement whereby the gas generators can be kept separate from other components of the system during manufacturing operations until as late in the assembly cycle as possible for optimum safety.